The present invention relates to a tip sharpening method as a probe manufacturing method usable for tunnel microscopes (STM), atomic force microscopes (AfM) and scanning proximity field optical microscopes (SNOM).
Conventionally, for usage in Sm and AFM there has been a demand for probes having a sharp form which is small in tip diameter and angle in order to obtain high resolution. On the other hand, in SNOM there has been a demand for a tip which is large in taper angle in order to improve the optical throughput at the probe tip. An interface etch method is utilized for sharpening an STM probe, while a method is used for an AFM probe that a sharp tip is formed by side etching effected under an on-silicon mask pattern. An optical fiber thermal drawing method and an etch method are used for a SNOM probe. In particular, the etch method includes a method to form a predetermined tip form by changing the composition of an etch solution and utilizing a difference in etch rate between the optical fiber core and the clad and a method developed by Turner et al. U.S. Pat. No. 4,469,554, 1984) to form a sharpened tip in an interface of two liquid layers wherein an organic liquid is placed on a hydrogen fluoride solution.
Each of the sharpening methods so far has been basically limited to a large extent in controlling the tip angle. For example, the optical fiber thermal drawing method has somewhat allows reduction or the tip angle but it is difficult to increase the tip angle and decrease the tip diameter according to that method. With the etch method, it is difficult to change the tip form without largely changing the etch condition including changing the probe material composition or the etch solution or etch gas composition. Also, according to the two-layer etch method a change in the taper angle is possible by changing the type of organic solvent. However, it is difficult to change the taper angle largely or obtain an arbitrary taper form. For this reason, the present invention provides a probe sharpening method capable of forming an arbitrary taper angle of a probe tip.